The background check system can determine if a potential gun buyer has a criminal history, but there is no safeguard to verify whether the name or identification being used by the buyer is valid, the General Accounting Office investigation found.

As a result, the current system "cannot ensure that the prospective purchaser is not a felon," the study said.

Rep. Henry A. Waxman (D-Los Angeles), who sought the undercover investigation, said the findings point to a problem with laws meant to prevent criminals from purchasing weapons.

"The name [on the identification] could be Bugs Bunny and as long as there's no criminal record on file the gun can be sold," said Waxman, the top Democrat on the House Government Reform Committee.

The National Rifle Assn., which is usually at odds with Democrats who favor gun control, agreed that identification checks are a problem.

"Unless you know the person standing in front of you is who they purport to be, then background checks are worthless," said Jim Baker, the chief lobbyist for the NRA.

Baker said the NRA supports better screening for driver's licenses and other state-issued IDs that are used for gun purchases but not additional screening for gun purchasers alone.

Democrats said the report provides fresh evidence for gun-control legislation. But the prospects seem dim: President Bush was supported by the NRA, and Congress generally is pro-gun rights.

Agents from the GAO, the investigative arm of Congress, were able to buy guns from licensed dealers in Virginia, West Virginia, Montana, New Mexico and Arizona.

Those states conform to the minimum requirements of the federal Brady law, which made gun buyers subject to background checks. But they have no additional state gun-control measures, such as fingerprinting.

Virginia and Arizona are point-of-contact states, meaning that background checks are done at the state and federal levels.

Officials at the GAO used off-the-shelf software and laminators to create counterfeit driver's licenses, inventing fictitious names, Social Security numbers and dates of birth.

Two undercover agents then went to randomly selected gun stores and pawnshops where they filmed their purchases of rifles, handguns, semiautomatic weapons, pistols, ammunition clips and hollow point bullets.

The agents told committee members at a hearing that they were sold guns every time they tried.

In one case in Santa Fe, N.M., when the background check did not provide immediate clearance for the undercover agent, the gun dealer suggested that the second agent could purchase the gun and transfer it to his partner.

Federal law prohibits dealers from knowingly selling weapons to individuals who are not buying the weapons for themselves or as a gift, and the case was referred to the Bureau of lcohol, Tobacco and Firearms.

In Tucson, the dealer suggested that the agent purchase a .38-caliber revolver from 1893 because background checks are not needed for buyers of antique guns.

Investigators also bought weapons from dealers in Richmond, Va.; Berkeley County, W. Va.; and Billings, Mont. The names of the gun dealers were not provided.

The background check system is run by the FBI. Officials at the Justice Department said they were reviewing the report.